<?php
function thongbao($c)
{
    ?>
    <script type="text/javascript">
        alert("<?php echo $c; ?> ");
    </script>
<?php
}
function trangtruoc()
{
    ?>
    <script type="text/javascript">
        window.history.back();
    </script>
    <?php
    exit();
}
function chuyentrang($link)
{
    ?>
    <script type="text/javascript">
        window.location="<?php echo $link; ?>";
    </script>
    <?php
    exit();
}
?>